1. Field of the Invention
The present invention relates to a method and composition for the topical treatment of diabetic neuropathy. More particularly, the present invention relates to a topical composition including a combination of ingredients that provide a surprising degree of effective relief from the symptoms of diabetic neuropathy and to a method for administering the topical composition to treat diabetic neuropathy.
2. Description of the Prior Art
Diabetes mellitus is a common disease that is usually classified into insulin-dependent and non-insulin dependent types. Both types may be managed by diet, in combination with insulin in the first type and a variety of drugs in the second type. However, while the changes in blood glucose associated with diabetes can usually be managed reasonably satisfactorily by conscientious patients and doctors, this does not prevent long term damage to many tissues as a result of the disease. This damage may take many forms but the major types are damage to the eyes (retinopathy), nerves (neuropathy), kidneys (nephropathy) and cardiovascular system,
There are many approaches to reducing or preventing these forms of damage, which are collectively known as the long-term complications of diabetes. One approach is based on damage that results from over-production of the glucose metabolite, sorbitol, in the cells of the body, Glucose can be converted to sorbitol by the enzyme aldose reductase. High levels of sorbitol may be among the causes of diabetic complications such as diabetic neuropathy. As a result, a number of pharmaceutical companies have been developing aldose reductase inhibitors for the purpose of reducing diabetic neuropathy.
It has been established that a wide variety of flavanoids are effective inhibitors of aldose reductase, including such flavanoids as quercetin, quercetin and myrecetrin. However, U.S. Pat. No. 4,232,040 discloses that despite the fact that these flavanoids have been shown in in vitro studies to be among the most potent flavanoids for aldose reductase inhibition, a need exists for aldose reductase inhibitors that can be more effectively used and in lower doses than the prior art compounds, including these flavanoids.
In fact, numerous patents are devoted to goal of developing improved aldose reductase inhibitors. Among these patents are U.S. Pat. Nos. 6,069,168; 5,011,840; 4,210,667; 4,147,795; 5,866,578; and 5,561,110. Numerous other patents also exist which relate to aldose reductase inhibitors.
Another approach to the treatment of neuropathy is disclosed in U.S. Pat. No. 5,840,736 (Zelle et al.). In this method, pharmaceutical compositions for stimulating the growth of neurites in nerve cells comprising a neurotrophic amount of a compound and a nerve growth factor. These compositions may be administered in a number of ways including orally and topically.
Still another approach to the treatment of neuropathy is disclosed in U.S. Pat. No. 5,550,249 (Della Ville et al.). In this approach, compositions suitable for treatment of vitamin H deficiencies are administered for the treatment of neuropathy. This patent relates to biotin salts with alkanolamines. The compositions may be administered orally, parenterally or topically.
U.S. Pat. No. 5,665,360 (Mann) relates to the treatment of peripheral neuropathies associated with diabetes mellitus by periodic topical application of a composition containing capsicum oleoresin as the active ingredient. When applied to the skin of the affected area, pain and burning associated with the neuropathy are said to be reduced. However, capsicum oleoresin has been shown to kill nerve endings in some cases and thus this composition suffers from this disadvantage.
U.S. Pat. No. 5,981,594 (Okamoto et al.) relates to a method of treatment of diabetic neuropathy using combined administration of a formulation including as an active ingredient, a prostaglandin I derivative with an anti-diabetic agent in order to improve nerve conduction velocities. Suitable anti-diabetic agents include oral hypoglycemic agents and insulin.
The Okamoto patent also contains a detailed discussion of the various types of neuropathy that may be associated with diabetes. According to this patent, nerve conduction velocity (NCV) is the most widely used method of objectively evaluating the severity of diabetic neuropathy. This patent also mentions that current methods of treating diabetic neuropathy such as dietetic therapy, administration of insulin, administration of aldose reductase inhibitors or aminoguaninidine to improve abnormal glucose metabolism, administration of troglitazone or agents for the improvement of blood flow have been tested but found to be insufficient when a single drug was used. Also, according to this patent, methods of treatment by combined use of different therapeutic agents which have different functions had yet to be established. The patent concludes that combined drug therapies for diabetic neuropathy, aiming at recovering once reduced nerve conduction velocity, have not yet been confirmed.
There remains a need in the art for an effective treatment for diabetic neuropathy that does not suffer from the disadvantage that it causes severe side effects, as do many aldose reductase inhibitors, for example.
Accordingly, it is the primary object of the present invention to provide a topical composition that is effective for the treatment of diabetic neuropathy.
It is another object of the present invention to provide a topical composition for the treatment of diabetic neuropathy which does not cause serve side effects in the patients treated with the composition.
These and other objects of the present invention will be apparent from the summary and detailed descriptions of the invention which follow.
In a first aspect, the present invention relates to a topical composition for the treatment of diabetic neuropathy. The composition comprises a cold compounded mixture of a compound that promotes synthesis of nerve growth factor, an aldose reductase inhibitor and an antioxidant formulated in a pharmaceutically acceptable carrier. It has been found that this combination of active agents provides significant, effective relief of the symptoms of diabetic neuropathy, as well as at least partial recovery of lost neurological function in some cases. In view of the consensus in the art that effective combinations of various active agents have not been demonstrated to be effective for the treatment of diabetic neuropathy, the present invention provides a surprising and unexpected effect. In addition, the topical compositions of the present invention, when used in effective amounts to treat diabetic neuropathy, do not exhibit the severe side effects of many prior art compositions proposed for treatment of this ailment,
In a second aspect, the present invention relates to a method for the topical administration of a composition in accordance with the present invention for the treatment of diabetic neuropathy. In the method, an effective amount of the composition of the invention is topically administered to the areas of the body that have been adversely affected by the diabetic neuropathy on a regular basis over a period of time sufficient to provide the beneficial effects of relief from the symptoms and at least some recovery of the damaged nerve tissues.
In a third aspect, the present invention relates to a pharmaceutically acceptable carrier for topical compositions that provides excellent dispersions and/or solutions of active ingredients and good penetration through the skin to the areas to be treated. The carrier for topical compositions may also include one or more materials that provide beneficial properties to the skin since many sufferers from diabetic neuropathy develop skin problems such as ulcers, lesions or cell damage.
In a first aspect, the present invention relates to a topical composition for the treatment of diabetic neuropathy. The composition includes a compound that promotes synthesis of nerve growth factor, an aldose reductase inhibitor and an antioxidant formulated in a pharmaceutically acceptable carrier for a topical composition.
The compound that promotes synthesis of nerve growth factor may be selected from suitable compounds that have been shown to have this activity. Suitable compounds that promote synthesis of nerve growth factor are those that do not induce significant, adverse side effects when topically applied to a patient in amounts that promote synthesis of nerve growth factor, and which do not react with one or more of the ingredients of the topical composition resulting in a substantial loss of activity of one or more active ingredients. Preferred compounds for promoting synthesis of nerve growth factor are those that occur naturally in the human body and/or materials obtained from plants or animal which may be ingested or topically applied by humans without significant, adverse side effects in the amounts used or derivatives thereof
Exemplary compounds that promote synthesis of nerve growth factor are vitamin D3, vitamin D3 derivatives such as 1(S), 3(R)-dihydroxy-20(R)-(1-ethoxy-5-ethyl-5-hydroxy-2-heptyn-1-yl)-9, 10-seco-pregna-5(Z), 7(E), 10 (19)-triene. The preferred nerve growth factor used in the topical composition is vitamin D3. Also, pharmaceutically acceptable salts of the compounds that promote synthesis of nerve growth factor may be employed.
The compound that promotes synthesis of nerve growth factor is used in an amount effective to promote the synthesis of nerve growth factor of about 10,000 to about 3 million IU. per kg of the composition. More preferably, the compound that promotes synthesis of nerve growth factor is employed in an amount of about 50,000 to about 2 million IU per kg of the composition, and most preferably an amount of 100,000 to about 1 million IU is used per kg of the composition.
The preferred compounds that induce synthesis of nerve growth factor may, in addition to this activity, also function to prevent neurotrophic deficits. This additional effect of the preferred compounds may also contribute to the overall beneficial effect of the topical composition of the present invention.
In order to formulate the compound that promotes synthesis of nerve growth factor in the topical composition of the present invention, it may be necessary to use a dispersant. Suitable dispersant materials are known to persons skilled in the art. A particularly suitable dispersant for the compounds that promote synthesis of nerve growth factor is corn oil. Corn oil also has the advantage that it is a natural product. The amount of corn oil used is an amount sufficient to disperse the compound that promotes synthesis of nerve growth factor.
The second active ingredient of the topical composition of the present invention is an aldose reductase inhibitor. Numerous suitable aldose reductase inhibitors are known to persons skilled in the art. Again, suitable aldose reductase inhibitors are those that do not induce significant, adverse side effects when topically applied to a patient in an amount effective for aldose reductase inhibition, and which do not react with one or more of the ingredients of the topical composition resulting in a substantial loss of activity of one or more active ingredients of the composition. Preferred aldose reductase inhibitors are those that occur naturally in the human body and/or materials obtained from plants or animal which may be ingested or topically applied by humans without significant, adverse side effects in the amounts used or derivatives thereof
As mentioned above, numerous aldose reductase inhibitors are known to persons skilled in the art. However, significant adverse side effects are associated with the use of many aldose reductase inhibitors in humans. Thus, it is important to select one or more aldose reductase inhibitors for use in the topical composition of the present invention based on minimizing the risk associated with use of the aldose reductase inhibitor taking into account the amount of that particular inhibitor that must be employed to achieve the desired level of aldose reductase inhibition. Different aldose reductase inhibitors exhibit different levels of inhibition. With this in mind, the preferred aldose reductase inhibitors for use in the topical compositions of the present invention are flavonoids and flavonoid derivatives. Exemplary aldose reductase inhibitors include (xe2x88x92)-epigallocatechin; (xe2x88x92)-epigallocatechin-gallate; 1,2,3,6-tetra-o-gallyol-xcex2-d-glucose; 2xe2x80x2o-acetylacetoside; 3,3xe2x80x2,4 -tri-o-methyl-ellagic acid; 6,3xe2x80x2,4xe2x80x2-trihydroxy-5,7,8-trimethoxyflavone; 6-hydroxy-luteolin; 6-hydroxykaempferol-3,6-dimethyl ether; 7-o-acetyl-8-epi-loganic acid; acacetin; acetoside; acetyl trisulfate quercetin; amentoflavone; apiin; astragalin; avicularin; axillarin; baicalein; brazilin; brevifolin carboxylic acid; caryophyllene; chrysin-5,7-dihydroxyflavone; chrysoeriol; chrysosplenol; chrysosplenoside-a; chrysosplenoside-d; cosmosiin; xcex4-cadinene; dimethylmussaenoside; diacerylcirsimaritin; diosmetin; dosmetin; ellagic acid; ebinin; ethyl brevifolin carboxylate; flavocannibiside; flavosativaside; genistein; gossypetin-8-glucoside; haematoxylin; hispiduloside; hyperin; indole; iridine; isoliquiritigenin; isoliquiritin; isoquercitrin; jionoside; juglanin; kaempferol-3-rhamnoside; kaempferol-3-neohesperidoside; kolaviron; licuraside; linariin; linarin; lonicerin; luteolin; luetolin-7-glucoside; luteolin-7-glucoside; luetolin-7-glucoronide; macrocarpal-a; macrocarpal-b; macrocarpal-d; macrocarpal-g; maniflavone; methy scutellarein, naringenin; naringin; nelumboside; nepetin; nepetrin; nerolidol; oxyayanin-a; pectolinarigenin; pectolinarin; quercetagetin; quercetin; quercimertrin; quercitrin; quercitryl-2xe2x80x3 acetate; reynoutrin; rhamnetin; rhoifolin; rutin; soutellarein; sideritoflavone; sophoricoside; sorbarin; spiraeoside; trifolin; vitexin; and wogonin. The most preferred flavonoid and/or flavonoid derivative aldose reductase inhibitors are quercetin, quercetrin, myricetin, kaempferol and myrecetrin since these compounds exhibit a high level of aldose reductase inhibition in combination with a relatively low toxicity. Also, pharmaceutically acceptable salts of these aldose reductase inhibitors may be employed.
The flavonoids and flavonoid derivatives are also preferred since some of these compounds may provide additional beneficial effects in the composition of the present invention. For example, quercetin may act as a chelator for transition metals that some studies have linked to certain symptoms of diabetic neuropathy. Flavonoids may also have some anti-inflammatory activity and/or may help stabilize cell membranes, both of which activities may be beneficial in the treatment of diabetic neuropathy.
The aldose reductase inhibitor is used in an amount of about 2 to about 40 grams per kg of the composition. More preferably, the aldose reductase inhibitor is employed in an amount of about 5 to about 30 grams and most preferably an amount of 8 to about 20 grams per kg of the composition.
Another active ingredient in the composition of the present invention is the antioxidant. The antioxidant may be a single compound or a mixture of two or more compounds. Also, the antioxidant may include one or more compounds that provide additional beneficial effects beyond the antioxidant activity, such as aldose reductase inhibition,
Compounds which may be used as antioxidants are those which exhibit antioxidant activity when administered topically without causing any severe adverse side affect when used in an amount effective to provide sufficient antioxidant activity, and which do not react with one or more of the ingredients of the topical composition resulting in a substantial loss of activity of one or more active ingredients. Preferred antioxidants are those that occur naturally in the human body and/or materials obtained from plants or animal which may be ingested or topically applied by humans without significant, adverse side effects in the amounts used or derivatives thereof
More preferred antioxidants are selected from ascorbyl palmitate, ascorbic acid (vitamin C), vitamin A, vitamin E acetate, xcex1-lipoic acid, especially DL-xcex1-lipoic acid, coenzyme Q10, glutathione, catechin, glangin, rutin, luteolin, morin, fisetin, silymerin, apigenin, gingkolides, hesperitin, cyanidin, citrin and derivatives thereof which exhibit antioxidant activity. Even more preferably, mixtures of two or more antioxidants are employed in the composition of the present invention. Particularly preferred antioxidant mixtures are ascorbyl palmitate with one or both of vitamin A and vitamin E acetate. The antioxidants may also be used in the form of their pharmaceutically acceptable salts and this may be preferred in some cases to increase solubility or dispersability, to reduce adverse side effects, etc.
The antioxidant is used in an amount of about 1 to about 50 grams per kg of the composition. More preferably, the antioxidant is employed in an amount of about 2 to about 30 grams, and most preferably an amount of about 5 to about 20 grams per kg of the composition.
The antioxidants used in the composition of the present invention are preferably selected not only for their antioxidant activity, but also based on other beneficial effects that particular compounds may provide. For example, ascorbyl palmitate not only has antioxidant activity, but also may act as an aldose reductase inhibitor and may help prevent degradation of nitric oxide (NO) and thus is a particularly preferred antioxidant for the present invention. Similarly, vitamin E may also help prevent degradation of nitric oxide and is thus a preferred antioxidant. Vitamin A is a fat-soluble material and thus is preferred for use due to this additional beneficial property. However, due to its solubility characteristics, vitamin A may need to be formulated in a suitable dispersant such as corn oil in much the same manner as vitamin D3 as described above,
Suitable additional beneficial properties for compounds useful in the compositions of the present invention include absorbability when applied topically, aldose reductase inhibition, antioxidant properties, free radical scavenging, transition metal chelation, nitric oxide stabilization, and anti-inflamatory activity.
The compositions in accordance with the present invention may provide one or more of the following beneficial effects to a patient when topically applied in effective amounts; relief of pain, burning, tingling, electrical sensations and/or hyperalgesia, increased microcirculation, nitric oxide stabilization, promotes healing of skin ulcers and lesions, protein kinase C inhibition, decreased oxidative stress, anti-inflammation, protection against radiation damage, particularly ultraviolet radiation, blockage of the formation of leukotrienes, stabilization of cell membranes, and promotion of the synthesis of nerve growth factor.
The method of the present invention involves the topical application of a composition of the present invention to areas of the skin in the vicinity of tissue that suffers from diabetic neuropathy. In particular, the present invention is useful on the patients"" extremities such as the fingers, toes, hands and feet where diabetic neuropathy is often the most pervasive.
In the method, a suitable amount of the composition of the invention is applied one to six times daily as needed to relieve pain and other symptoms of the diabetic neuropathy. Preferably, the composition is applied two to four times daily, as needed for pain. A sufficient amount should be applied to cover the area afflicted with the diabetic neuropathy with a thin layer of the composition and the composition should be rubbed into the skin until little or no residue remains on the skin. Treatment begins initially to treat acute symptoms but may be continued indefinitely to relieve pain, prevent symptoms of diabetic neuropathy from returning and possibly restore some nerve and/or skin function.
The method of the present invention may provide one or more of the beneficial effects described above for the compositions of the invention. In addition, the method of the present invention may provide some additional beneficial effects due to one or more of the ingredients contained in the pharmaceutically acceptable carrier as described in more detail below,
The pharmaceutically acceptable carrier of the present invention is suitable for use as a carrier for topical compositions wherein the active ingredients are dissolved, dispersed and/or suspended in the composition. The carrier of the present invention contains at least a hydrophilic ointment base, panthenol or a panthenol derivative and a dispersant if needed to disperse one or more insoluble or partially insoluble active ingredients in the carrier.
Suitable hydrophilic ointment bases are known to persons skilled in the art. Exemplary hydrophilic ointment bases suitable for use in the present invention are non-U.S.P. hydrophilic ointment bases such as those made by Fougera, Inc. Sufficient hydrophilic ointment base is employed to act as a Garrier for the active ingredients of the composition. Typically the hydrophilic ointment base will make up more than about 80% of the total composition and more preferably about 80-90% of the composition is the hydrophilic ointment base. The hydrophilic ointment base functions as a carrier and enhances penetration into the skin.
The panthenol or panthenol derivatives useful in the present invention include at least D-panthenol, DL-panthenol and mixtures hereof This component of the carrier has skin moisturizing properties and acts as a quick, deep penetrating component of the carrier that helps deliver the active ingredients through the skin to the area to be treated and imparts a healing effect to damaged tissue. The amount of panthenol or panthenol derivative to be employed is from about 0.25 to about 10 weight percent, more preferably from about 0.5 to about 5 weight percent and most preferably from about 1 to about 2 weight percent, based on the total weight of the composition.
The carrier of the present invention may also include additional ingredients such as other carriers, moisturizers, humectants, emollients dispersants, radiation blocking compounds, particularly UV-blockers, as well as other suitable materials that do not have a significant adverse effect on the activity of the topical composition. Preferred additional ingredients for inclusion in the carrier are sodium acid phosphate moisturizer, witch hazel extract carrier, glycerine humectant, apricot kernal oil emollient, and corn oil dispersant.
Other materials which may optionally be included in the topical compositions of the present invention include inositol, other B-complex vitamins, and anti-inflammatory agents. The composition of the present invention may also be employed to facilitate wound healing, for the treatment of skin cancer and/or one or more symptoms thereof or as a composition for protecting skin from the harmful effects of radiation such as radiation breakdown.
The composition of the present invention is made by cold compounding. This is an important feature of the invention since one or more of the compounds employed in the topical composition are sensitive to heat or other types of energy and thus the activity of the composition may be detrimentally affected as a result of the formulation of the compositions in other manners. Thus, the ingredients of the topical composition the present invention are merely mixed together, without heating using a sufficient amount of the carrier to provide a substantially homogeneous cream or ointment. It may be necessary to dissolve, disperse or suspend one or more of the ingredients prior to cold compounding in order to ensure substantially homogeneous distribution of the active ingredients in the composition.
A preferred composition of the invention can be made using the following ingredients, all based on use of one pound of hydrophilic ointment base. 25-35 cc of a 50% aqueous solution of sodium acid phosphate moisturizing agent, 5-10 cc of D- or DL-panthenol, 5-10 cc of glycerine, 1-3 cc of apricot kernal oil, 3-5 cc of a dispersion of vitamins A and D3 in a corn oil base, 10-20 cc of witch hazel extract, 0.5-2 cc of vitamin E acetate, 2-4 grams of ascorbyl palpitate and 4-8 grams of quercetin powder. Optionally, one or more of the glycerin, witch hazel extract, vitamins A and E and/or the ascorbyl palmitate can be reduced or eliminate from a particular composition, if desirable or larger amounts of one type of component, i.e. antioxidant, can be employed while reducing the amount of another component of the same type or having a similar type of activity,
The invention will now be further illustrated by the following example.